Ski boots, ice skates and in-line skates are currently used which have a shell constituted by a front portion and a separate rear portion, which are mutually slidingly associated in order to allow the user to change the length of the shell. This solution allows to adapt the shoe to the particular morphological characteristics of the user and/or to achieve a change of size which allows said known types of shoe to be worn even by users who have feet of different sizes or by children who over time will change foot size rapidly.
For example, EP-A-1714570 and US-2006-0230638-A1 disclose a ski boot which comprises a standardized rigid sole from which a shell protrudes in the region of the forefoot and approximately up to the arch region, the shell being open toward the heel region, a counter being slidingly associable with said shell in a rear region and interacting with means for adjusting and guiding the axial position with respect to the sole, a quarter whose height can be adjusted being rotatably associated therewith.
However, this known type of ski boot, while allowing to vary the length of the shell and the height of the quarter, so as to be able to adapt to the specific size of the foot and of the leg of the user, has a drawback: between the shell and the counter there can in fact be plays which may allow the penetration of snow or water into the boot, with the consequent user discomfort that this entails.
Further, since the shell is provided in two components, the strength and stability of this known type of ski boot are limited.
Italian utility model patent No. 00251472 discloses a sports shoe, particularly a skate with inline wheels or an ice skate whose size is adjustable, which is constituted by a tip and a separate heel unit, with which a first support and a second support for one or more wheels or an ice-skating blade are associable or rigidly coupled respectively in a lower region, said supports being provided with means for mutual longitudinal sliding.
Means for connecting and adjusting the mutual axial position which can be activated by means of a retractable lever are provided between the tip and the heel unit.
This known type of skate also has the same drawbacks observed in the previous background art.